This invention relates to detecting bacteria.
Bacteria are identified in a variety of ways. Many have characteristic forms which can be seen under microscopic examination, but some are identified, when colonised on a growth medium, by a characteristic colour and in some cases this is confirmed by smell. Not all bacteria have any appreciable odour, but many have a characteristic associated gas or vapour due to their inherent metabolic activities.
Patent Abstracts of Japan, application number JP-A-60130398, discloses a detector for detecting the presence of microorganisms on the basis of evolved gases. WO 94/04705 discloses a method of detecting E. Coli by monitoring a gaseous product, this gaseous product being produced by cleavage of a glucuronide conjugate by xcex2-glucuronidase produced by a certain bacterial species. GB-A-2176901 describes gas sensors based on the use of semi-conducting organic polymers, whilst U.S. Pat. No. 4,456,380 discloses an optical bacteria identification system using a plurality of optical filters.
The invention comprises a method for identifying bacteria comprising detecting gas or vapour associated with the metabolic activity of the bacteria and differentiating such gas or vapour from gas or vapour associated with other bacteria.
The method may comprise abstracting gas or vapour from a detection region and flowing the same over an array of sensors of which an electrical property varies according to exposure to gases or vapours and observing the response of the sensors.
The sensors may comprise semi-conducting polymers the resistance or impedance of which varies according to exposure to gases or vapours.
The response of the sensors may be compared against a library of responses to known bacteria, or the response may be input to a neural net trained against known bacteria.
The detection region may comprise an enclosed space above a Petri dish or like laboratory culture dish.
The array of sensors may first be purged using a purging gas.
The invention also comprises apparatus for detecting bacteria comprising detector means for detecting a gas or vapour associated with the bacteria.
Said detector means may comprise an array of sensors of which an electrical property varies according to exposure to gases or vapours. The sensors may comprise semi-conducting polymers the resistance or impedance of which varies according to exposure to gases or vapours.
The apparatus may comprise a store for a library of responses to known bacteria and comparison means operable automatically to compare a given response against the library. The apparatus may also comprise a neural net the input to which comprises the array of sensors and which is trained against known bacteria.
The apparatus may comprise a probe for sampling a detection region by abstracting gas or vapour from said region to be passed to said detector means. Said probe may comprise a cover for enclosing a Petri or like laboratory culture dish or an area of growth medium thereon.
Said probe may comprise a carrier gas feed and return and the apparatus may comprise a source of carrier gas.